In order to assess the effects of specific genes on premalignant progression in vivo, we have generated transgenic mice in which the tetracycline regulatable transactivators tTA and rTA are targeted to the epidermis with a keratin 5 promoter. THese mice have been crossed with a transgenic line containing a tetO regulated constitutively active TGFb. In mice containing both the BK5/tTA and tetOTGFb1 transgenes, high levels of expression of TGFb1 produces an embryonic lethal phenotype. Partial suppression with suboptimal levels of doxycycline generates full term but nonviable mice. The neonatal lethal phenotype is characterized by runting, hypoplastic epidermis and atrophy of the hair follicles. Complete suppression of TGFb1 expression allows for normal embryonic development. However, if double transgenic mice are removed from doxycycline after weaning, the mice undergo progressive alopecia at the onset of the second hair cycle. Associated with the alopecia is significant follicular hyperplasia and focal inflammation. If the mice are returned to doxycycline, hair regrows within 2-3 weeks. The long term goal of this project is to identify genes differentially regulated by TGFb1 in normal and neoplastic epidermis. We are currently using this inducible system in conjunction with cDNA microarray analysis to identify genes that are regulated by TGFb1 in the normal epidermis. Cluster analysis of microarray data shows distinct patterns of gene regulation. Verification of these patterns and determination of significance is underway.